1. Field of the Invention
The present invention relates to a jet-propulsion personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a personal watercraft having a cruising control function.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercrafts have been widely used in leisure, sports, rescue activities, and the like. The personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a hull bottom surface and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
Many of the personal watercrafts are small straddle-type watercraft capable of carrying one to three riders. Since such watercraft have high driving (turning) performance, a throttle operation is commonly performed by a throttle lever provided in the vicinity of a grip of a bar-type handle.
Since such personal watercrafts are jet-propelled, they are capable of cruising even in shallow waters. Therefore, bases for the personal watercraft (facilities equipped with launching slopes) are commonly located in inland areas distant from general boat cruising areas. While cruising in the shallow waters or at a certain distance from the base, the personal watercraft needs to be cruising at low speeds. In some countries, the water areas requiring low-speed cruising are specified by regulations (e.g., in US, about 5 mile/h equal to about 8 km/h).
During cruising in the shallow waters at low speeds, it is required that the rider continue to operate the throttle lever with high maneuverability at an engine speed slightly higher than an idling speed, which increases rider""s operating discomfort. The rider sometimes needs to keep squeezing the throttle lever for a long time. This is also required in the case where the personal watercraft is cruising for a long time at medium or high speeds, for example, the personal watercraft is utilized as a transport means in a water tour.
As a related prior art, Japanese Laid-Open Patent Application Publication No. 10-29595 discloses a device for performing control so that hump state in a medium speed area where non-planing state switches to planing state can smoothly switch to the planing state. In general, when the engine speed is increased/decreased for the purpose of maintaining a constant cruising speed in the hump state, resistance of the body of the watercraft relatively greatly increases/decreases. In particular, when the watercraft is temporarily planing and the resistance of the body greatly decreases, the engine speed becomes too high, i.e., rapid increase in the engine speed occurs.
The present invention addresses the above-described condition, and an object of the present invention is to provide a personal watercraft having a cruising control function capable of cruising at a constant cruising speed or engine speed without a need for a rider to continue to perform a throttle operation, i.e., an operation which opens/closes the throttle.
Another object of the present invention is to prevent rapid increase in an engine speed.
These objects are achieved by the jet-propulsion personal watercraft constituted as described below.
A jet-propulsion personal watercraft according to the present invention comprises: a water-jet pump including an outlet port and a steering nozzle, the water jet pump pressurizing and accelerating sucked water and ejecting the water from the outlet port to propel the watercraft as a reaction of the rejecting water; and a cruising control operation means, and the watercraft is controlled to cruise at a predetermined cruising speed or a predetermined engine speed in accordance with an operation of the cruising control operation means.
In the jet-propulsion personal watercraft so constituted, the rider merely operates the cruising control operation means, thereby maintaining the predetermined cruising speed or engine speed without a need for the rider to perform the throttle operation. This increases rider""s steering comfort in the case where the watercraft is cruising at low speeds for a long time or at medium speeds for a long time in a water tour or the like.
It is preferable that, in the personal watercraft, the cruising control operation means is attached to a handle of the watercraft.
This makes it possible that the rider easily operates the cruising control operation means in a normal steering posture.
It is preferable that, in the personal watercraft, the predetermined cruising speed is set to a low speed of approximately 8 km/h or less. This is advantageous when the watercraft is cruising at low speeds for a long time.
It is preferable that, in the personal watercraft, the predetermined cruising speed or engine speed is set to a cruising speed or engine speed at a point of time when the cruising control operation means is operated. This facilitates cruising at a constant cruising speed or engine speed desired by the rider.
It is preferable that, in the personal watercraft, a plurality of predetermined cruising speeds or engine speeds are preset and the cruising control operation means is adapted to select one of the plurality of cruising speeds or engine speeds. This makes it possible that the watercraft is cruising at a desired cruising speed or engine speed during the water tour, etc.
It is preferable that, in the personal watercraft, the cruising control operation means is comprised of a switch. This is advantageous because the switch is easily operated by the rider and water-proof.
It is preferable that, in the personal watercraft, the switch is placed in the vicinity of a grip of the handle, because the switch is easily operated by the rider.
It is preferable that, the personal watercraft may further comprise: a cruising control OFF operation means, and control, i.e., cruising control for cruising the watercraft at the predetermined cruising speed or engine speed is released in accordance with an operation of the cruising control OFF operation means. The operation of the cruising control can be easily performed.
The personal watercraft may further comprise: a fuel supply unit for supplying fuel to an engine for driving the water jet pump; a throttle operation means for opening/closing a throttle of the fuel supply unit for regulating supply amount of the fuel; an actuator for opening/closing the throttle of the fuel supply unit; and a control means for controlling the actuator so that the watercraft cruises at the predetermined cruising speed or the predetermined engine speed, in accordance with an operation of the cruising control operation means, wherein the fuel supply unit is adapted to allow an opening of the throttle to be increased when one of the throttle operation means and the actuator drives the throttle to be opened, and the opening to be reduced when both of the throttle operation means and the actuator drive the throttle to be closed. With such constitution, the throttle operation means allows the throttle of the fuel supply unit to be opened/closed. Besides, when the cruising control operation means is operated, the control means controls the actuator to cause the throttle of the fuel supply unit to be opened/closed so that the watercraft cruises at the predetermined cruising speed or engine speed. Consequently, the cruising control can be executed in a suitable manner. The fuel supply unit may be a carburetor having a throttle for regulating supply amount of fuel to the engine, and the carburetor may be adapted to allow an opening of the throttle to be increased when one of the throttle operation means and the actuator drives the throttle to be opened, and the opening to be reduced when both of the throttle operation means and the actuator drive the throttle to be closed.
It is preferable that the actuator is mounted to a body of the personal watercraft. The actuator is hardly affected by the oscillation of the engine.
It is preferable that, the carburetor comprises a throttle valve fixed to a rotational shaft and rotating with the rotational shaft to cause an air flow passage of the carburetor to be opened/closed, a connecting member provided at one end of the rotational shaft so as to rotate with the rotational shaft, a rotary engagement member being rotatable coaxially with the rotational shaft, and a throttle pulley provided at the other end of the rotational shaft so as to rotate with the rotational shaft, the rotary engagement member can be brought into contact with an engagement portion of the connecting member by rotating relatively to the engagement portion in a rotational direction of the rotational shaft to cause throttle valve to be opened, the throttle pulley is rotated by the throttle operation means, and the rotary engagement member is rotated by the actuator. With such constitution, the throttle operation means allows the throttle of the carburetor to be opened/closed. Besides, when the cruising control operation means is operated, the control means controls the actuator to cause the throttle of the carburetor to be opened/closed so that the watercraft cruises at the predetermined cruising speed or engine speed. Consequently, the cruising control can be executed in a suitable manner. In addition, since the throttle operation means and the actuator are respectively connected to different end portions of the rotational shaft of the throttle valve, the carburetor can be installed without great spatial limitation.
The above and further objects and features of the invention will be more fully apparent from the following detailed description with accompanying drawings.